This invention relates to parts-handling apparatus and more particularly to an apparatus and method for feeding and positioning parts having a thin profile for assembly with an article.
Assembly machines are used to automatically assemble an article from its component parts. Injector razors, spark plugs, and light bulbs are but a few of the types of articles typically assembled by assembly machines. The assembly machines may be of the "rotary" type, such as disclosed in U.S. Pat. Nos. 3,065,530 and 3,231,968, assigned to the assignee of the present invention, or of the "in-line" type, such as disclosed in U.S. Pat. Nos. 2,887,209 and 2,990,940, also assigned to the assignee of the present invention.
Component parts for these articles assembled by such assembly machines often include relatively thin parts, having a cross-sectional dimension of less than one hundred mils (thousandths of an inch). These thin parts may be regular, circular washers or discs, or may have non-circular configurations or irregular central openings. Attempts have previously been made to position and feed thin parts consistently, accurately, and automatically to assembly machines. However such efforts have not always been fully successful.
Several problems arise in handling thin parts. Each part typically must be added to an article assembly one at a time. However, thin parts have a tendency to stick to one another because of the surface tension or capillarity of minute amounts of liquid, such as water or oil, that are usually present in the environment in which such parts are used. Also, parts with irregular central openings or peripheral edges tend to bunch up and interlock when fed in such a way that they pass across or on top of one another.
Prior attempts to handle, feed, separate and position such thin parts for pick-up include transverse feeding and stack feeding apparatus. Transverse feeding presented significant problems because of bunching and interlocking parts. Parts may bunch up because they are warped, have variances in thickness, or are otherwise malformed. Attempts to separate bunched or stuck parts by passing them under a gate or through a slot often failed because the parts were so thin that they clogged the gate or slot instead of being separated by it.
Known stack feeding apparatus for assembly machines include a slide feed with a straight stack and a floating arbor arrangement with a curved stack. A straight stack, slide feed arrangement is shown in FIGS. 1 through 5 of U.S. Pat. No. 3,231,968, particularly identified by reference numerals 12, 25, and 36. In the known floating arbor arrangement, washers were continuously fed on a U-shaped or J-shaped arbor to a separating means, such as a pair of opposed magnets, to operate on parts capable of being magnetized. Level sensors were also used to detect when the arbor needed to be reloaded with washers. The use of arbors generally requires parts having a uniform central opening on which the parts can be fed. If the arbor could be designed to accommodate an irregular opening in a part or a part with a slit passing through its center to its edge, then specific arbors had to be designed for particular parts and the general utility and applicability of the parts feeder and positioner using the arbor was limited. Also, arbors are not always suitable for holding parts that have relatively small openings in a stack arrangement. Arbors sometimes cannot be made strong enough to hold the weight of a plurality of parts on them.
Accordingly, the present invention overcomes disadvantages of the prior art by providing an apparatus and method that does not rely on a floating arbor or a slide feed arrangement for handling, feeding, and positioning thin profile parts. The apparatus and method of the present invention operate on thin parts with irregular central openings or peripheral edges and warped or otherwise malformed parts without substantial bunching, jamming, or interlocking. The present invention provide handling, feeding, and positioning of thin parts with simple and economical operation, versatility, and reliability in use. Other objects and advantages of the present invention will become apparent as the description of the invention proceeds.
Briefly, in accordance with the invention, there is provided an apparatus with a tube containing a number of thin parts in a stack arrangement, having a loading end and a dispensing end, a device for feeding parts to the separating device, from the loading end to the dispensing end of the tube, and a device positioned at the dispensing end of the tube for separating at least one of the parts from the remainder of the parts and positioning the part at the dispensing end of the tube for pick-up. Thus, parts are separated one at a time which facilitates handling of the part to the article assembly. Even if the parts have a tendency to stick together because a foreign substance is lodged between them, the separating device of the present invention is designed to separate the parts. Furthermore, parts with irregular shapes and designs may now be reliably, economically, and easily fed to machines to assemble articles.
Preferably, the length of the tube is straight or J-shaped. The J-shaped tube may be used to invert a part. The feeding means in the preferred embodiment includes brake means to control movement of the parts along the tube and sensing means for measuring the number of parts located at the separating means. The sensing means in the preferred embodiment includes photoelectric detector means for receiving a light beam projected through the tube which generates a signal for releasing the brake means. Also, the separating means in the preferred embodiment includes at least two like magnetic poles generating a magnetic field across the dispensing end of the tube. The intensity of the field is sufficient to induce repulsive magnetic forces in the parts so that they do not contact each other.
In keeping with the present invention, a method for feeding and positioning a thin part to be grasped by a pick-up device is provided, which includes stacking thin parts in a tube, separating one of the parts from the stack, positioning the part at the end of the tube for pick-up, and feeding more parts to the separating step. Thus, a simple and economical method allows articles to be manufactured without elaborate equipment. Yet, the problems previously discussed are alleviated. Also, the method may include removing the positioned part from the end of the tube and placing the part on an assembly table.
Preferably, the stacking step includes vibrating the parts out of a hopper and directing the parts into the tube. The separating step of the preferred embodiment includes generating a magnetic field between like poles of a magnet and applying the field to the parts. Also, the feeding means of the preferred embodiment includes disposing brake means to control movement of the parts in the tube, measuring the number of parts at the separating step by receiving a light beam projected through the tube with photoelectric detector means and generating an output signal, releasing the brake means, and re-engaging the brake means when the number of parts increase to a preset limit.
While the invention will be described in connection with preferred embodiments, it will be understood that it is not intended to limit the invention thereto, but rather to cover all modifications and alternative constructions falling within the spirit and scope of the invention as broadly defined. The invention will be further described in conjunction with the appended drawings.